Heat stress (HS) conditions in broiler farms impair antioxidant markers (total antioxidant capacity, catalase, superoxide dismutase, and malondialdehyde) and immune indices (IL1β, IFN-γ, IL10, and C3), which reflected negatively on productivity, resulting in economic losses. Therefore, we used 300 Cobb-500 broiler chicks were used to evaluate the impacts of early heat conditioning (EHC) and dietary glutamine (DG) on their productive and immunological traits. In a completely randomized factorial design (2 × 3), 300 Cobb-500 broiler chicks underwent EHC (40 vs. 32 ◦ C) at 5 days post-hatch for 24 h and were fed DG (0, 0.4, or 0.6 %) during their first week of rearing. The impact of HS up to 35 days post-hatch was investigated (humidity temperature index, 82–91). Each treatment was replicated ten times. EHC and DG had positive effects on broiler productivity (BW at 35 days of age increased by 4.4 % and feed conversion rate values decreased by 1.9 %). Similar effects were observed for the proteinogram and metabolite constituents, lipid profiles, immune indices, antioxidant markers, and HSP70. Moreover, there were no differences in most traits between the two DG treatments (chicks fed 0.4 and 0.6 % glutamine). The results suggest synergistic effects of EHC and DG in improving broiler productivity and enhancing their physiological, antioxidant, and immune statuses under HS conditions. EHC at 5 days post- hatch for 24 h and DG supplementation during the first week of the rearing period, either separately or com bined, may minimize the harmful effects of HS on broiler chickens.